There are two kinds of charging methods in an electrophotographic apparatus such as a laser printer, a duplicator, and a facsimile. One of the charging methods is a corona charging method which attaches ions or electrons, without contacting, to an outer peripheral surface of a rotary drum type photosensitive member, as disclosed, for instance, in FIG. 2.4 from pages 48 to 53 of "Base and Application of Electrophotographic Technique" published on Jun. 15, 1988 by Corona Co. in Japan. The other method is a contacting type conductive brush charging method, as disclosed, for instance, in FIG. 2.8 of the above-mentioned "Base and Application of Electrophotographic Technology".
Further, a development counter having charge electrodes is disclosed, for instance, in U.S. Pat. No. 4,450,220 issued on May 22, 1984 and entitled "Method of charging electrostatic developer". Referring to FIGS. 7 and 8 of U.S. Pat. No. 4,450,220, they disclose that the toner powder is applied to the charging space formed between the charging member and the sleeve and then the electrostatic image developed on the sleeve is transferred to the rotary drum type photosensitive member.
The contactless type corona charging method, as in the conventional electrophotographic apparatus mentioned above, has the following drawback. When ions or electrons are attached on the surface of the rotary drum type photosensitive member, the performance and durability of the photosensitive member are remarkably deteriorated and the quality of print is affected adversely, since the photosensitive member is affected by ozone or corona ions generated at the corona discharge. An ozone filter, which is made up of an activated carbon and a strong fan, have to be supplied for removing the generated ozone, which has strong offensive odor, and exhausting the ozone. Since high voltage of 3000-4000 volts has to be provided for the charging corona, there are problems of environmental sanitation, high power demand, and danger of receiving an electric shock. The contacting type conductive brush charging method mentioned above has a drawback that the surface of the rotary drum type photosensitive member is worn out.
The development counter having charge electrodes mentioned above is different from the electrophotographic apparatus of the present invention in its principle of operation, as is apparent from the explanation below.